LIBGDX:从另一个类调用矩形会导致NullPointerException吗？

Question

PlayScreen类：

public class PlayScreen implements Screen {

private Player player;
private OrthographicCamera camera;
private OrthogonalTiledMapRenderer renderer;
private TiledMap map;
private Rectangle rightRectangle, leftRectangle, playerRectangle;


@Override
public void render(float delta) {
    Gdx.gl.glClearColor(0, 0, 0, 1);
    Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

    renderer.render();

    renderer.getSpriteBatch().begin();
    player.draw(renderer.getSpriteBatch());
    renderer.getSpriteBatch().end();
}

@Override
public void resize(int width, int height) {
    camera.viewportWidth = width;
    camera.viewportHeight = height;
    camera.update();

}

@Override
public void show() {
    camera = new OrthographicCamera();
    map = new TiledMap();
    renderer = new OrthogonalTiledMapRenderer(map);

    player = new Player(new Sprite(new Texture("img/player.png")), playerRectangle);
    playerRectangle = player.rectangle;
    rightRectangle = new Rectangle(1280,0,0,720);
    leftRectangle = new Rectangle(0,0,0,720);


    boolean wallLeft = leftRectangle.overlaps(player.rectangle);
    boolean wallRight = rightRectangle.overlaps(player.rectangle);


    if(wallLeft){
        System.out.println("wallLeft Overlap");
        player.velocity.x = 0;
    }
    else if(wallRight){
        System.out.println("wallRight Overlap");
        player.velocity.x = 0;

    }

    player.setPosition(Gdx.graphics.getWidth()/2f - player.getWidth()/2f,Gdx.graphics.getHeight()/2f - player.getHeight()/2f - Gdx.graphics.getHeight()/5f);

}

@Override
public void hide() {
    dispose();
}

@Override
public void pause() {

}

@Override
public void resume() {

}

@Override
public void dispose() {
    map.dispose();
    player.getTexture().dispose();
    renderer.dispose();

}

}

玩家等级：

public class Player extends Sprite{

public Vector2 velocity = new Vector2();
private float speed = 500;
public Rectangle rectangle;


public Player(Sprite sprite, Rectangle rectangle){
    super(sprite);
    this.rectangle = rectangle;

}

public void draw(SpriteBatch spriteBatch){

    update(Gdx.graphics.getDeltaTime());
    super.draw(spriteBatch);
}

public void update(float delta) {

    rectangle = new Rectangle(getX() + velocity.x * delta,0,286,160);

    setX(getX() + velocity.x * delta);

}

}

所以，我正在使用矩形来检测我的碰撞。我已经设置了右矩形和左矩形作为我屏幕的边界线。我想给玩家分配一个精灵和一个矩形。我正在处理PlayScreen类中的碰撞，但它导致了NullPointerException。需要帮助来弄清楚为什么我得到了NullPointerException。

谢谢！

空指针异常：

Exception in thread "LWJGL Application" java.lang.NullPointerException
    at com.badlogic.gdx.math.Rectangle.overlaps(Rectangle.java:210)
    at net.dermetfan.asteroids.screens.PlayScreen.show(PlayScreen.java:62)
    at com.badlogic.gdx.Game.setScreen(Game.java:62)
    at net.dermetfan.asteroids.screens.MainMenu$1.clicked(MainMenu.java:75)
    at  
        com.badlogic.gdx.scenes.scene2d.utils.ClickListener.touchUp(ClickListener.java:82)
    at com.badlogic.gdx.scenes.scene2d.InputListener.handle(InputListener.java:57)
    at com.badlogic.gdx.scenes.scene2d.Stage.touchUp(Stage.java:329)
    at com.badlogic.gdx.backends.lwjgl.LwjglInput.processEvents(LwjglInput.java:297)
    at 
     com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:209)
    at    
       com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)

Answer 1

问题出在你的playerRectangle。

player = new Player(new Sprite(new Texture("img/player.png")), playerRectangle); // playerRectangle not initialized!
playerRectangle = player.rectangle;
rightRectangle = new Rectangle(1280,0,0,720);
leftRectangle = new Rectangle(0,0,0,720);

试试这样的东西

    playerRectangle=new Rectangle(x,y,w,h);
 player = new Player(new Sprite(new Texture("img/player.png")), playerRectangle); 
    playerRectangle = player.rectangle; // i don't even think you should put this line is useless
     rightRectangle = new Rectangle(1280,0,0,720);
        leftRectangle = new Rectangle(0,0,0,720);

现在你不应该有任何错误。

或者最好在玩家类中这样做，在主类中不需要玩家矩形

    public Player(Sprite sprite){
    super(sprite);
    this.rectangle = sprite.getBoundingRectangle();

}

在你的班上

   player = new Player(new Sprite(new Texture("img/player.png")));        
         rightRectangle = new Rectangle(1280,0,0,720);
            leftRectangle = new Rectangle(0,0,0,720);